Receiver for space signaling.



No. 770,228. PATENTED SEPT. 13, 1904. L. DE FOREST.

RECEIVER FOR SPACE SIGNALING.

APPLICATION FILED DBO. 24. 1902.

H0 MODEL.

w/rlvzssfEs; /NVEN 70/? 8) MLM g a Patented September 13, 1904.

PATENT @EETEE.

LEE DE FOREST, OF NEW YORK, N. Y.

RECEIVER FOR SPACE SIGNALING.

SPECIFICATION forming part of Letters Patent No. 770,228, dated September 13, 1904.

Application filed December 24, 1902. S rial No. 136,434. (No model.)

T 0 a whom it may concern.-

Be it known that I, LEE DE FoREs'r, a citizen of the United States, and a resident of the city of New York, borough of Manhattan, in the county and State of New York, have invented certain new and useful Improvements in Receivers for Space Signaling, of which the following is a specification.

My invention relates to an improved form of automatic current-operated receivers, and comprises the parts and combination of parts hereinafter described,and particularly pointed out in the claims.

I have found that if two or more members consisting alternately of materials which are unlike such, for instance, as steel and aluminium-be placed in series in the aerial circuit a strong autocoherer effect is produced. These members should preferably be of slight mass, a convenient form for securing this being to make them as line needles or rods. If the contact pressure between adjacent members be adjustable and maintained by a flexible spring at considerable pressure, the sensitiveness of the device is increased. I secure this result by employing a spring to support one member in contact with the others and provide means for adjusting the tension of the spring, and therefore the contact-pressure. possesses qualities which especially adapts it to such use. It is a well-known fact that a fresh and clean aluminium surface exposed to the air will almost instantaneously be acted upon by the oxygen of the air to form a very thin film of oxid of aluminium, which then protects the mass of the metal against further oxidation. It therefore possesses inherent capabilities of automatic self-restoration of the insulating-film after it has been broken down or destroyed by passage of the signaling impulse.

The figure of drawing accompanying herewith and forming a part of this application shows my invention in a form now preferred by me.

The sensitive parts of the receiver shown consist of needles or fine rods, which are alternately of aluminum and steel and are held in contact by a spring or other like means,

I have found that aluminium which may be adjusted so as to vary the contact-pressure. As herein shown, two steel needles 0 are used, supported in contact with the under side of aluminium rods or pins D by a spring E, which is supported by a thread I or other flexible suspending member from a rotatable adjusting-rod G, the latter being frictionally held in adjusted position by its bearing support H. Any other suitable method of adjustment of the spring tension may be employed. The collecting-antenna A may be connected with one of the rods or pins D and the ground or earth connection E with the other. The local circuit, which includes the battery B and the indicating instrument T, herein shown as a telephone-receiver, is

here directly connected with the pins or rods D that is, no choke-coils are employed. IVhile in some cases choke-coils may be desirable, I have found that in general they are unnecessary with this low-resistance and ourrent-operated device. I have shown two needles connecting the pins; but a greater or less number may be used. I have found that two or three No. 8 steel needles give very satisfactory results. I have also found it advantageous to slightly roughen the contact-surfaces, as by filing the aluminium pins. This increases the sensitiveness'of the device. I have also found that a slight film of a non-conducting or poorly-conducting material at the point of contact, forming a slight insulation, improves the working of the device. For such coating I have used liquid coatings of an oleaginous nature and at times have mixed with it a fluid of an electrolyzablc character, as water. The conductivity in this case is therefore electrolytic. The thin film of electrolyte between the two opposing members is decomposed by the sudden passage of the Hertzian oscillations. Minute bubbles or a film of gas is thereby generated, whereby the resistance of the device is suddenly increased; but this is automatically reduced upon the cessation of the I-Iertzian oscillation exactly as is described in United States Patent No. 716,000. If the fluid used be' of a somewhat viscous character, as an oil, it is better retained in place, and hence is more reliable in its action.

It is evident that the relative position of the aluminium and steel members may be reversed without affecting the principle or the action of my device.

I have found that such a device as is above described is very sensitive to the electric waves, but is little affected by those causes which tend to produce a microphonic action. Sounds or mechanical disturbances cause little or no effect upon the indicating device. It is also very reliable in its action, easily adjusted, and not easily thrown out of adjustment. I prefer also that it be not inclosed, but be left where it is readily accessible, so that the points of contact between the parts may be changed whenever desired.

The advantages of the fluid film herein spoken of is not limited to the combination of aluminium and steel members or to aluminium alone. Both of the contacting sensitive members may be of the same metal, and this need not be aluminium. It may, for example, be of tin. Aluminium, however, seems better adapted to this use than most metals in the form of receiving apparatus herein described. I do not, however, wish to be understood as limiting this feature of my invention to its application to aluminium members.

Having thus described my invention, what I claim, and desire to secure by Letters Patent, is

1. A wave-sensitive member comprising two poles, a connecting-rod and spring means for supporting said rod in contact with the under side of the poles.

4. A wave-responsive receiver comprising members in series in the aerial circuit and alternately consisting of steel and aluminium, said aluminium members having roughened contacting surfaces. I

5. In wireless telegraphy a receiver comprising contacting members, one of steel and the other of roughened aluminium, and a film of an electrolyte covering the contacting surfaces of said members.

6. An anticoherer comprising contacting members, one of steel and the other of aluminium, and a film covering the contacting surfaces and consisting of a non-conducting fluid having an electrolyzable liquid mixed therewith.

In testimony whereof I have hereunto aflixe d my signature,this 17th day of December, 1902, in the presence of two witnesses.

LEE DE FOREST.

Witnesses:

H. L. REYNoLDs, ERNEST KNIGHT SATTERLEE. 

